Circulators have a wide variety of uses in commercial, military, space, terrestrial, and low power applications, and high power applications. A waveguide circulator may be implemented in a variety of applications, including, but not limited to, low noise amplifier (LNA) redundancy switches, T/R modules, isolators for high power sources, and switch matrices Such waveguide circulators are important in space applications (for example, in satellites) where reliability is essential and where reducing size and weight is important.
Moving parts wear down over time and have a negative impact on long term reliability. Circulators made from a ferrite material have high reliability due to their lack of moving parts. Thus, the highly reliable ferrite circulators are desirable for space applications.
Waveguides may be the best electro-magnetic transmission media for the circulator in order to provide low insertion loss or to allow for a switchable direction of circulation. However, the waveguide circulator may need to directly interface to components in other transmission media, such as coaxial or microstrip line. An example of one such component is an LNA. LNAs are implemented on microstrip transmission line, and may have microstrip or coaxial interfaces. Therefore, a transition from a waveguide to a microstrip or to a coaxial line is required between the waveguide circulator and each LNA.